A conventional wheelchair may be considered to include a patient support unit and a wheelchair base. The support unit is formed of the seat bottom and seat back on which the patient's body rests. The wheelchair base includes the wheels, casters, and other structural elements.
Conventional wheelchairs have been designed to accommodate and enhance the mobility of the users. For instance, many wheelchairs are designed so that they can be folded up easily. This allows the user of a wheelchair to travel in a car while storing the wheelchair conveniently in the trunk or in the back seat.
Wheelchairs have been designed to accommodate different size patients. They come in different widths and have different wheel bases depending upon the needs of the patient. In addition, wheelchairs have been provided with accessories to support patients. For example U.S. Keropian Pat. No. 3,640,571 shows a pair of thoracic and lumbar supports to support a patient with scoliosis.
Patients with severe deformities have had seats custom formed to fit their bodies. These cushions have been made by forming a plaster impression of the patient's body and using that impression to make a mold in which a custom foam cushion is subsequently formed. Custom foam cushions made in this way have some disadvantages. They cannot be changed once they are manufactured, so they do not accommodate a patient's growth easily. In addition, they do not easily accommodate changes in patient's size as when winter clothing is necessary. When stretching vinyl over the custom shaped foam, the vinyl may develop weaknesses which wear out prematurely. Moreover, when a wheelchair with a custom seating system is no longer needed, it has often been discarded even though the wheelchair base is still functioning well.
For these reasons a need remains for a seating system which can be installed on previously used wheelchair bases and which can be readily adjusted to accommodate the changing physical needs of a patient or, when no longer needed by one patient, can be adjusted to the different physical needs of another patient.